1. Field of the Invention
This invention relates to an apparatus for fabrication of cementitious building blocks, and more particulary to an apparatus for casting cementitious building blocks with special channels therein for containment of thermally insulative material.
2. Description of the Prior Art
As a result of the current interest in energy conservation, the well known cementitious building block, which has been used for many years in the construction arts, has become the subject of much criticism due to its lack of thermally insulative properties, and this has resulted in many attempts to improve the heat transfer characteristics of such blocks.
One prior art technique employed to improve the heat transfer characteristics of cementitious blocks includes the filling of the vertical passages formed through the block with insulative material. This does improve the heat transfer characteristics of the block somewhat, but the benefit derived is limited in that the end walls and center rib wall of each block remains uninsulated and thus, a finished wall built of these blocks has a multiplicity of uninsulated cementitious thermally conductive passages extending transversely therethrough. While this technique does improve the thermal energy characteristics somewhat, it causes further problems in that the vertical passages of the blocks, which are often used as passageways for plumbing, wiring, wall reinforcing bars, cementitious grouting and the like, can no longer be so used due to the presence of the insulative material, which if omitted from selected passageways will reduce the thermally insulative properties of the finished block wall.
Another prior art attempt at improving the thermally insulative characteristics of cementitious blocks includes the casting of inwardly facing notches in the end walls and center rib wall of otherwise conventionally configured blocks. Two prefabricated, rigid planar members of insulative material are manually inserted into the blocks so as to be held in place by the special notches. This locates the inserted members so that each spans a different one of the vertical passages of the blocks. This prior art attempt at improving the insulative properties of cementitious blocks has the same shortcomings as the previously described technique of filling the verticl passages with insulative material in that the block's end walls and center rib wall remain good conductors of thermal energy and the vertical passages are at least partially blocked.
Continuing attempts to provide cementitious blocks with substantially improved thermally insulative properties progressed from the above described prior art techniques to cementitious blocks which are cast in various special configurations for containing insulative barriers that are in turn cast in place within the special blocks. In general, these special blocks are cast with a channel extending through the block. The channel, which may be centrally located or offset toward one of the vertical sidewalls of the block, are parallel to the sidewalls of the block and are of substantially equal size with respect thereto. When the block is fully cured, insulative foam is cast within the channel so as to become an integral part of the block. In theory this is ideal in that the insulative foam barrier extends the full length and height of the block thus retarding heat transfer between the opposite vertical sidewalls or faces, of the block. However, in actual practice this technique causes some problems with the production of the blocks themselves and further problems with the casting of the insulative foam in the special blocks.
With regard to the casting of the special blocks, it will be appreciated that they cannot be cast without some means for interconnection of the block parts which are separated by the channel which will subsequently contain the insulative foam barrier. In the absence of interconnecting structure or structures, the separated block parts will simply be free to move relative to each other. In this situation the desired shape of the block will be difficult if not impossible, to maintain during casting, transporting, and curing of the block itself, and would need special positioning and supporting structures when the insulative foam is being cast in the channel.
In view of this need for block part interconnection, one prior art special cementitious block was cast with a U-shaped channel formed in at least one of its vertical sidwalls so that interconnection was provided by the closed bottom which defined the channel. This configuration was quickly discarded in that the lack of support at the upper ends of the U-shaped channel resulted in sagging of the block parts.
Another prior art special block was provided with a spaced pair of relatively thick structural interconnecting walls which were equally spaced along the length of the channel and extended from the open bottom of the channel to a point about half way to the top of the channel. To provide sufficient interconnecting support of this particular prior art block, the two interconnecting structural walls were relatively thick and thus, the resulting block was provided with two large cementitious passageways which were good conductors of thermal energy.
As hereinbefore mentioned, the prior art special blocks which were cast with the channels therein also presented problems with regard to the casting of insulative foam therein. As is known, some insulative foams, such as polystyrene, have little or not adhesive properties, i.e., they will not adhere to the cementitious surfaces. Thus, such foams will add little or no structural strength to the interconnected parts of the block which define the channel and therefore the interconnection members must be either increased in number or size, and such increases defeat the objective of improving the thermal insulative properties of the block.
A particular insulative foam, namely, polyurethane foam is well known to be an excellent insulator and is a highly tenacious material in that it will form a very strong bond when cast and cured in contact with virtually anything. Polyurethane foam is the ideal material for use in the especially cast blocks in that it will add considerable structural strength to the special blocks and thus allow the use of a minimum number and minimum size of the interconnecting members. This tenacious characteristic of polyurethane foam however, causes production problems when cast in the channels of the above described prior art special cementitious blocks. The open ends, and in some instances, the open or at least partially open, bottoms of the channels cast in the prior art special blocks must be temporarily closed during the casting of the polyurethane foam within the channels. The polyurethane foam will form a strong bond with the channel closing members just as it does with the block surfaces, and thus without the application of some sort of a releasing agent, the channel closing members are very difficult, if not impossible, to remove without destroying the product or the channel closing members. The use of a releasing agent is costly, time consuming, and not entirely satisfactory. The channel closing members must be recoated with the releasing agent prior to each use, and even with such recoating, production must be interrupted periodically to grind off the polyurethane foam which invariably adheres to the channel closing members at locations of inadequate application of the releasing agent.
Further, in production operations, complex and costly equipment is needed to position the channel closing members and firmly hold them in place against the pressures exerted by the curing polyurethane foam. And, the channel closing members must tightly close the otherwise open channels in that the curing polyurethane foam will escape through any cracks, gaps or other openings and stick to anything it comes in contact with. It is virtually impossible to completely close the sides and bottom of the block's channel due to manufacturing tolerances. For example, the channel closing members may completely close the channel of one block, and be a loose fit in the channel of subsequent blocks.
The above described shortcomings and problems which have been encountered in the prior art attempts to produce a thermally efficient cementitious block have been overcome, to a great extent, in a particular block which is fully disclosed in U.S. patent application Ser. No. 109,520, filed on Jan. 4, 1980 by the same inventor. Briefly, this special block includes a cementitious block of substantially conventional configuration which is cast with an open top channel in at least one of its vertical sidewalls or faces. The bottom of the channel is closed by a thin-wall web or skin, and the opposite end of the channel are similarly closed. Thin-wall stabilizer webs are also provided in spaced increments between the block parts which are separated from each other by the channel. The thin-wall webs provide the needed interconnection of the separated block parts, and the bottom and end closing thin-wall webs or skins, allows polyurethane foam to be cast within the block's channels, thus eliminating the need for external channel closing members.
To the best of my knowledge, none of the above described prior art special blocks have achieved any appreciable amount of commercial success in that the above described production problems associated with casting of the blocks per se, and subsequent in-block casting of the insulative foam panels have kept these prior art blocks from being economically mass produced. Since the prior art blocks have not solved the inherent production problems, it is believed that no sophisticated production equipment has been developed or suggested, and it is further believed that such equipment has not been developed or suggested for the production of the specific special block disclosed in the hereinbefore referenced U.S. patent application Ser. No. 109,520, filed on Jan. 4, 1980.